Investigation: Choosing Wires To Do Different Jobs In Electrical Engineering.

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Introduction

John Harvey 11 Aquin

SC1 Investigation: Choosing Wires To Do Different Jobs In Electrical Engineering.

TASK!

My task is to find out whether the resistance of a wire changes or is affected the longer the piece of wire is.

BACKGROUND KNOWLEDGE!

WHAT IS RESISTANCE?

Electricity can only be conducted through a conductor, like the wire I will use in my experiment. Electricity is allowed to flow because of the free electrons in the wire. Depending on what material is used depends on how many electrons it has, and more free electrons means less resistance. Gold is not reactive, but it is a far better conductor of electricity than iron, because it has more free electrons. The free electrons ‘absorb’ the energy transmitted via the current and move, and collide with other free electrons. This reaction will continue to happen, and that is what allows electricity to be conducted. Resistance happens because energy is lost as heat, so the hotter a wire will become, the more resistance there would be due to increase heat escaping. The resistance occurs when free electrons collide with the fixed particles in a metal, and other free electrons. These collisions will happen so fast and hard, that some of the energy will be lost as heat, therefore creating the resistance.

HOW TO MEASURE RESISTANCE.

The resistance within a wire is measured by calculating the current in the series and the voltage across the wire, which is in parallel. The calculations can then be made when using the below formula:

TABLE TO SHOW AVERAGE RESULTS FROM EXPERIMENT ON WIRE 1, SET 1 AND WIRE 1, SET 2

LENGTH

VOLTAGE 'V'

CURRENT 'A'

RESISTANCE (2d.p.) Ω

AVERAGE RESISTANCE (2 d.p) Ω

10CM WIRE 1 SET 1

0.66

1.22

0.54

0.52

10CM WIRE 1 SET 2

0.51

1.02

0.50

20CM WIRE 1 SET 1

0.84

0.89

0.94

0.96

20CM WIRE 1 SET 2

0.79

0.79

0.97

30CM WIRE 1 SET 1

0.97

0.70

1.39

1.40

30CM WIRE 1 SET 2

0.91

0.65

1.40

40CM WIRE 1 SET 1

1.06

0.57

1.86

1.86

40CM WIRE 1 SET 2

1.02

0.55

1.85

50CM WIRE 1 SET 1

1.16

0.50

2.32

2.29

50CM WIRE 1 SET 2

1.08

0.48

2.25

60CM WIRE 1 SET 1

1.22

0.44

2.77

2.76

60CM WIRE 1 SET 2

1.15

0.42

2.74

70CM WIRE 1 SET 1

1.25

0.38

3.29

3.26

70CM WIRE 1 SET 2

1.19

0.37

3.22

80CM WIRE 1 SET 1

1.27

0.35

3.63

3.67

80CM WIRE 1 SET 2

1.22

0.33

3.70

This is my first table of results for the resistance of a wire. As you can see I have tested the same wire twice, so that the results are varied. The resistance increases as the length of the wire increases, just I said it would in my prediction. However, although the results are proportionate, they are not directly proportionate. For example, take the 4th result. The resistance is 1.86Ohms. At 80cm it should be 3.72Ohms but it is 3.

some tests on the wirewere done when the wire was at a higher temperature than it was for others, therefore resulting in increased heat and more resistance. If I were to do the experiment again, I would probably experiment on the wires four times instead of two so that I got a larger variety of results, allowing me to have more data to analyse. Another thing I would do would be to take more care when measuring because the fact that I didn’t measure them properly means that the experiment was inaccurate. I believe that it would have been better if the wires were cut into 10, 20,30,40,50,60,70,and 80cm pieces. That would save me having to measure the wire and the results would be more accurate. The wires might also be straighter if they are smaller, because they won’t bend as easily. I would also prefer the experiment to be spread over two lessons because in testing two wires twice, which equates to four really, I did not have the time to continually take the battery out and put it back in like I said I would, in the beginning. That is why I also said that wire 1 was more accurate than wire 2. If I were to repeat the experiment again, I could have used a computer to record the results. This would rule out human error in being too slow to stop the stop clock once there is a reading. Using a computer would also I presume speed up the experiment so that more tests could have been done on wires?

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